$ { {-5} \times \left[\begin{array}{rr}{0} & {4} \\ {4} & {1}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-5}\times{0} & {-5}\times{4} \\ {-5}\times{4} & {-5}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {-20} \\ {-20} & {-5}\end{array}\right]}$